Manufacturers of hand-held and/or portable electronic devices, such as laptop computers, personal digital assistants (PDA), wireline or wireless telephones, video games and other similar electronic devices, continually strive to add new features and applications to their products. Many of these new features and applications require, or can be enhanced by, the ability to enter text directly into the device, instead of downloading the text from another device, such as a computer or server. For example, the majority of wireless telephones on the market today offer a text messaging application and a phone book feature, both of which require text entry directly into the device.
The prevailing text entry method in wireless telephones is the existing twelve-key numeric pad, which is used to input 10 decimal digits and 26-33 characters of the alphabet, depending on the language. Multiple alpha-numeric characters are assigned to each key, and selection of a particular character requires the user to potentially press a key multiple times at a certain pace. Although the keypad text entry method does enable a user to enter text directly into an electronic device, the keypad text entry method is slow and has a fairly long learning curve.
Another text entry method available in some electronic devices is a software-defined keyboard (“soft keyboard”) displayed on the electronic device display. Soft keyboards can be either pen-based, in which the user employs a stylus to tap and select a key, or cursor-based, in which the user moves a cursor to a desired key using a navigation (or cursor control) device on the electronic device and selects the key by pressing a “Select” button, an “Enter” button or another similar selection mechanism.
One traditional cursor control device for controlling the position of a cursor on a display is a four-directional rocker-switch (e.g., arrow buttons). With a rocker-switch, the user selects a particular key on the soft keyboard by using the arrow buttons to move through a Manhattan grid of characters on the display. Although such traditional cursor control devices are highly accurate, rocker-switch cursor control devices suffer from slow text entry speed. Another type of cursor control device that provides improved speed over traditional cursor control devices is an omni-directional analog pointing device, such as a puck-type pointing device. Puck-type pointing devices are compact puck-shaped devices that may be manipulated by a user's finger to move within a puck field of motion. The position of the puck in the puck field of motion is sensed using a variety of electrical, electromagnetic and optical techniques, and the position of the puck is mapped to a cursor position on a display.
Examples of puck-type pointing devices are described in U.S. Pat. No. 6,084,570 to Milroy, entitled “Compact Cursor Controller Structure For Use With Laptop, Notebook and Hand-Held Computers and Keyboards,” U.S. Pat. No. 5,771,037 to Jackson, entitled. “Computer Display Cursor Controller,” U.S. Pat. No. 6,278,440 to Katsurahira et al., entitled “Coordinate Input Apparatus and Position-Pointing Device,” and U.S. patent application Ser. No. 10/723,957 to Harley et al., entitled “Compact Pointing Device.”
For analog-type cursor control devices (e.g., puck-type pointing devices) using soft keyboards, the speed of text entry depends on both the accuracy of the cursor control device and the size of a target key on the display. For a given accuracy of a cursor control device, the speed of text entry can be increased by enlarging one or more soft keys on the display. Various solutions have been proposed to enlarge keys on the display, thereby increasing the speed of text entry. For example, one proposed solution is a variable-width soft keyboard, in which the size of the key representing a letter is proportional to the frequency of use of that letter. For example, in the proposed solution, the frequently used e-key appears approximately five times larger than the rarely used z-key.
Although variable-width soft keyboards do significantly increase the text entry speed, increasing the width of a key improves the probability of contacting the key only in one direction. In addition, depending on the dexterity of the user, the difficulty in contacting the smaller keys (e.g., z, q, etc.) may offset the gain provided by the larger keys to an unpredictable degree. Therefore, what is needed is a key enlarging solution for a soft keyboard that increases the probability of selecting any key in any direction.